This invention relates to injection devices and methods of assembly thereof. In particular, but not exclusively, the invention relates to automatic or semi-automatic pen-type injectors where the user dials in a dose by rotating a ratcheted dose setting knob by a desired angular amount, thereby straining a torsion spring. On release of the ratchet, the consequent rotation causes expression of a dose of a preset volume. Typical examples of such devices include our widely available Autopen® pen injector and other injectors of the type described in U.S. Pat. No. 5,104,380.
In the assembly of such devices the introduction, alignment and securing of the torsion spring within the housing is normally done by hand because skill is required to achieve correct assembly. With the increasing numbers it is not cost-effective to assemble such devices by hand and so some form of automatic assembly is required. However, automatic assembly devices are not capable of assembling in the same manner as heretofore. A need exists for a spring anchorage which is well suited for automatic assembly, allowing rapid installation by an automated assembly machine.